Re: Fwd: ebtables broken for kernel above 2.6.28

[sachin sanap <sachin.sanap.1gb@gmail.com>]

Sorry dint inform you earlier that iam on 32bit ARM machine.
The real problem is the kernel is computing the alignment on
__alignof__(struct _xt_align) and the userspace ebtables is computing
it on __alignof__(struct ebt_entry_target) , which are two different
structs.

I have the following patch for ebtables-v2.0.8-2 that fixes this.



--- ebtables-v2.0.8-2.orig/include/ebtables_u.h 2009-05-29
21:41:32.000000000 +0530
+++ ebtables-v2.0.8-2/include/ebtables_u.h      2009-05-29
21:43:32.000000000 +0530
@@ -25,6 +25,7 @@
 #define EBTABLES_U_H
 #include <netinet/in.h>
 #include <linux/netfilter_bridge/ebtables.h>
+#include <linux/netfilter/x_tables.h>

 #ifndef IPPROTO_SCTP
 #define IPPROTO_SCTP           132
@@ -37,7 +38,7 @@
 #define EXEC_STYLE_DAEMON      1

 #ifndef EBT_MIN_ALIGN
-#define EBT_MIN_ALIGN (__alignof__(struct ebt_entry_target))
+#define EBT_MIN_ALIGN (__alignof__(struct _xt_align))
 #endif
 #define EBT_ALIGN(s) (((s) + (EBT_MIN_ALIGN-1)) & ~(EBT_MIN_ALIGN-1))
 #define ERRORMSG_MAXLEN 128


-Sachin




On Fri, May 29, 2009 at 3:32 PM, Jan Engelhardt <jengelh@medozas.de> wrote:
>
> On Friday 2009-05-29 07:51, sachin sanap wrote:
>
>>Iam facing problem with ebtables binay on 2.6.28 kernel (same binary
>>works well with 2.6.27). Its mostly a structure alignment issue with
>>standard targets like DROP,ACCEPT etc. Message seen by user is
>>"eb_tables: standard target: invalid size 8 != 4"
>>Iam trying to fix it, this mail is just to check if its already fixed
>>by someone else?
>
> Indeed this seems to happen, but only when using a mixed-bitness
> combination:
>
> /tmp/usr/sbin # LD_LIBRARY_PATH=../lib ./ebtables -A INPUT -j ACCEPT
> The kernel doesn't support the ebtables 'filter' table.
>
> /tmp/usr/sbin # uname -a
> Linux sovereign 2.6.29.3-jen80-default #1 SMP 2009-04-06 18:10:58 +0200
> x86_64 x86_64 x86_64 GNU/Linux
>
> /tmp/usr/sbin # file ebtables
> ebtables: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), for
> GNU/Linux 2.6.4, dynamically linked (uses shared libs), stripped
>
> ebtables does work when it is 64-bit too, so the immediate workaround —
> assuming you are on x86 — is to not use a 32-bit userspace with a
> 64-bit kernel.
>
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